Hi d3adgurl, welcome to the forums
Most of the information you need to answer this dot-point is in fact in your textbook, but it's hard to work out what is being asked so that you can apply your knowledge.
Let's begin by breaking the requirements of the question into three parts.
1) What was the technology that preceded the transistor, and what were its shortcomings?
2) Which materials were tested as possible replacements for valves and why?
3) Compare the advantages and disadvantages of valves and transistors, and perhaps a sentence about the invention of the transistor.
1)
(copied from my notes, which were made from CSU and elsewhere)
In electrical appliances there is often a need to control the direction of current flow, convert AC to DC, switch current flow on or off or amplify a current
Before the invention of the transistor, these tasks were performed with thermionic devices (valves)
Thermionic devices use heated filaments and terminals in glass vacuum tubes, heating the filament to liberate electrons which are then accelerated to the anode by a high potential difference
Shortcomings thermionic devices were inefficient, expensive and unreliable
Inefficient valves developed a large amount of heat, requiring surrounding equipment to be thermally insulated
Expensive - very large, needed lots of meterials
Unreliable - valaves are very fragile, if the vacuum is lost then they break. As they are made out of glass....
2) Germanium - I no longer remember the details, except that it was easily extracted from its ore and did not have to be very pure to be a semiconductor, unlike silicon. I do remember that Jacaranda has the details
.
3) I can't remember much about the invention of the transistor, but as for its advantages it does eveything thermionic devices do only better
. So mention all the faults of valves, and then say that transistors are the opposite
HTH
